The present invention relates to an actuating device for dispensing a paste-like material, especially in the dental field, from a capsule or cartridge, whereby the actuating device has an abutment for supporting the capsule or cartridge within the actuating device in the direction of dispensing.
Such an actuating device is known from U.S. Pat. No. 4,472,141. This actuating device comprises a handle which acts on a plunger by which a paste-like material for dental purposes is dispensed from a capsule or cartridge. According to U.S. Pat. No. 4,472,141, a threadable closure cap and an undercut in the form of a counter collar are provided at the capsule or cartridge which are connected to the forward end of the actuating device. The force to be applied by the handle onto the plunger and thus onto the capsule or cartridge is, in general, a multiple of the manual force applied whereby due to the selected leverage ratio, for example, five times the manual force is applied to the paste-like material.
Since the spacing between the pressure application of the handle and its pivot axis surpasses the spacing between the pivot axis and the follower of the plunger, for example, by a factor 5, the applied plunger force can thus have a magnitude of one kN or even more. With respect to this force, there is the risk that the capsule or cartridge will break out of the comparatively thin screw cap or will deform in the area of the counter collar such that a safe supporting action is no longer possible. This is true especially when the screw cap is not securely applied because then it is not ensured that the capsule or cartridge is properly supported with its counter collar between the undercut of the screw cap and a sealing ring or the forward end of the exterior thread. On the other hand, when manipulating the actuating device It is not always detectable whether the screw cap has been completely secured.
Another actuating device Is known from European Patent Application A1-63 891. This actuating device comprises a downwardly open channel in which the cartridge is secured. The cartridge is oversized relative to the sidewalls of the channel and, accordingly, the channel should be somewhat flexible in order to be able to introduce the cartridge from the open side.
This arrangement, however, has not been proven successful in practice. Due to the tight guiding of the counter collar within the channel, which is required for reasons of stability, the cartridge upon removal must be guided exactly parallel to the axis of the plunger present in the device. However, since it can be gripped only at its forward end, there is always the risk that the cartridge upon removal will jam and the counter collar of the cartridge will become jammed in the guide. The user then assumes that an increased actuating force must be applied which he can do without a problem, but will result in that the cartridge can break, resulting in undesirable contamination of the actuating device as well as of the surroundings. This is especially a problem when mercury-containing amalgam materials are used as a paste-like material in the dispensing or actuating device.
It is therefore an object of the present invention to provide an actuating device of the aforementioned kind which allows a safe actuation at high actuating forces with easy removal of the capsule or cartridge.